Blue Holly or Meserve Holly

(Aquifoliaceae - Holly Family)

Form

• medium-sized, broadleaf evergreen ornamental shrub
• maturing at approximately 8' tall by 8' wide, but highly variable depending upon the particular hybrid (some are wider than tall, while others are taller than wide, but many are pruned or sheared into a hedge, pyramid, or globe shape anyway)
• variable in growth habit from upright vased to open spreading to rounded, or can be sheared into pyramidal or rounded form
• slow growth rate (medium growth rate in optimum situations)

Culture

• full sun to full shade (best in partial sun to partial shade)
• prefers moist, well-drained, rich, slightly acidic soils, but tolerates soils of average to poor fertility and is pH adaptable to neutral or slightly alkaline soils (many Hollies require acidic soils)
• hybrids are propagated primarily by rooted stem cuttings
• Holly Family, with few disease or pest problems, but Winter leaf and stem burn may occur in Northern climates, and Summer heat stress will often occur in Southern climates
• plant one male plant for every three to five female plants, to ensure good pollination and fruit set on the female (berry-laden) plants
• abundantly available, primarily in containers, but also in ball and burlap form
• broadleaf evergreens (such as Blue Holly) should preferably not be planted at south- or west-facing exposed sites, in order to avoid Winter foliage burn (from the sun and wind) and Summer heat stress
• pruning of plants of either gender should carefully done, as too much pruning at too late a point in the season will remove nearly all of the floral buds for the following season, since the flower buds set by mid-July on the current season's growth

Foliage

• evergreen, waxy, alternate, and elliptical, with prominent spiny margins, to about 3" long
• most Blue Hollies have new foliage that emerges as a bronzed light green, quickly maturing to a dark waxy blue-green and persisting for about three years on the stems ('China Boy' and 'China Girl', however, have kelly green foliage and chartreuse stems)

Flowers

• dioecious (staminate and pistillate flowers occur on separate male and female plants), cream-colored, miniature, occuring in clusters in the leaf axils
• heavy flowering occurs in May on both genders (but sporadic flowering also occurs in Autumn, resulting in very limited fruit set) and is ornamentally insignificant
• during the dormant season, male plants have about twice as many "knobs" on each immature floral bud in each leaf axil (where each "knob" will become an individual flower in the overall inflorescence) as the female plants do
• identification of male and female plants is much easier when both are in flower, as the female flower will have a small green ovule (or pre-fruit) in the center of its white petals, while the male flower will have yellowish stamens (pollen-bearing structures) in the center of its white petals

Fruits

• subtle green berries mature to vibrant red (or yellow) berries on female shrubs in October, sometimes persistent until the following Spring (unless eaten by wildlife, or abscising in harsh Winters), but turning brown-black at some point in most Winters
• showy due to their excellent contrast against the evergreen foliage
• please note that a fruitless Blue Holly in Winter can be a male, or a female that was not pollinated, or a female that has possibly had all of its berries eaten or abscised; but, a plant with berries is always a female

Twigs

• most Blue Hollies have purplish-green to dark green stout stems that are ribbed, gradually changing to a greenish tan and slightly rough (however, 'China Boy' and 'China Girl' have yellow to chartreuse, relatively thin stems)

Trunk

• on old shrubs, trunks are slightly rough, tan, and often hidden by the lower branches

ID Summary

• spreading or upright shrub with waxy, spiny-margined, broadleaf evergreen foliage, having ribbed stems that are either purplish-green or chartreuse, and knobby Winter floral buds that open to ornamentally insignificant flowers on separate male and female plants in May, producing abundant fruits that ripen as red berries on female plants in October and persist throughout most of the Winter, effectively contrasted against the blue-green or green foliage

USAGE

Function

• foundation, group planting, understory, or specimen shrub; can also be a formal, informal, or barrier hedge, where the spiny broadleaf evergreen foliage serves as a kinder and gentler alternative to thorns

Texture

• medium-bold texture
• average to thick density, depending upon age and whether or not it has been sheared

Assets

• bluish waxy evergreen foliage
• showy red berries on female plants persist throughout Autumn and most of the Winter
• full sun to full shade adaptable
• attracts wildlife (primarily birds, which seek refuge in its spiny-foliaged evergreen canopy and may consume the fruits during the dormant season)

Liabilities

• foliage and stem burn in harsh Winters
• heat stress during especially hot and dry Summers
• moderately slow growth rate
• one male plant must be planted nearby for every three to five female plants, to ensure pollination and fruit set on female plants
• the male plant will almost always be more vigorous over time, and can overwhelm female plants if planted side-by-side
• improperly selected male cultivars often will not pollinate certain female cultivars due to misaligned flowering periods (named pairs are bred and released for this purpose)
• shearing of male and female plants will result in reduced bloom and fruit set for the following year

Habitat

• zones 5 to 8
• of several complex hybrid origins, depending upon cultivar; the parents generally are from Europe and Japan

SELECTIONS

Alternates

• shrubs with broadleaf evergreen foliage (Buxus hybrids, Ilex glabra, Ilex opaca, Mahonia aquifolium, etc.)
• shrubs with attractive Winter fruits (Ilex verticillata, Myrica pensylvanica, Viburnum opulus 'Compactum', etc.)
• shrubs with other attractive Winter features (Cornus sericea, Corylus avellana 'Contorta', Kerria japonica, Salix alba 'Britzensis', etc.)

Variants

• Meserve Hollies were originally bred by Mrs. Leighton Meserve of New York by using two species, Ilex rugosa (Prostrate Holly, a low and spreading shrub holly, for cold hardiness) and Ilex aquifolium (English Holly, a large tree holly, for foliage and berry beauty). Since her original introductions, either the same species or other species have been rehybridized or hybridized, respectively, and introduced as "Blue Hollies".
• Ilex x meserveae 'Blue Boy' & 'Blue Girl', 'Blue Prince' & 'Blue Princess', and 'Blue Stallion' & 'Blue Maid' are the three paired representatives of the true Meserve Hollies that are common today, noted for their dark blue-green foliage, purplish green stems, and red berries on the female plants. Of all the males, 'Blue Stallion' has the reputation of blooming over an extended period of time, and is therefore often used to pollinate any of the Blue Holly female plants, especially those of an unkown cultivar. A relatively new female introduction is 'Golden Girl', which has striking golden-yellow fruits (that are an even more effective contrast than the red-fruited forms against its blue-green foliage).
• Ilex x meserveae 'China Boy' and 'China Girl', a pair with distinctively lighter-green foliage and chartreuse stems, are the most heat tolerant and cold hardy, due to being the progeny of a cross between Ilex cornuta (Chinese Holly, a large holly noted for its heat tolerance) and Ilex rugosa (Prostrate Holly, a low spreading holly noted for its cold hardiness). They also grow slightly more rapidly, but do not have as heavy of fruit set and the dark blue-green foliage of other hybrids.
• It is a very good idea not to "mix and match" any named pairs of Holly cultivars within the dioecious hybrid Ilex x meserveae, since a mismatch of blossom times by even one week will result in poor to non-existent pollination and little or no fruit set on female plants; if a male counterpart in a named pair is not available, use 'Blue Stallion' as the male pollinator.

NOTES

Translation

• Ilex comes from the name of a species of Oak native to the Mediterranean.
• x meserveae is named after Mrs. Leighton Meserve, in honor of her plant breeding that created the original Meserve Holly (or Blue Holly) hybrids.

Purpose

• Blue Holly is the most cold-hardy broadleaf evergreen shrub with both attractive Winter fruits and waxy foliage.

Summary

• Ilex x meserveae is one of the best broadleaf evergreen shrubs for ornamental Autumn and Winter fruits (on female plants, usually red), and spiny-margined glossy foliage (generally blue-green), with an upright to spreading, medium-sized shrub habit that can be sheared into various shapes, including pyramidal form.